Field
Embodiments described generally relate to creping adhesives and methods for making and using same. More particularly, such embodiments relate to creping adhesives that include one or more thermosetting polyamidoamine-epihalohydrin resins and one or more thermoplastic polyamidoamine-epihalohydrin resins and methods for making and using same.
Description of the Related Art
The manufacture of paper is generally carried out by producing an aqueous slurry of cellulosic fibers and a variety of chemicals and subsequently removing most of the water to form a thin paper web. The structural integrity of the paper arises in large part from the mechanical entanglement of the cellulosic fibers in the web and hydrogen bonds that form between the cellulosic fibers. With paper intended for use as tissue and towel products such as facial tissue, bathroom tissue, paper towels, and napkins, the level of structural integrity arising from the paper-making process conflicts somewhat with the degree of perceived softness that is necessary for consumer acceptance of such products. The most common method of increasing the perceived softness of tissue and towel products is to “crepe” the paper. The creping action can impart a fine, rippled texture to the sheet, increase the bulk of the sheet, improve softness of the sheet, and/or improve absorbency of the sheet. Creping can be accomplished by affixing the moist, cellulosic paper web to a rotating thermal drum commonly known as a Yankee dryer, by applying the web onto the surface of the dryer, which has been sprayed with a creping adhesive, generally in the form of an aqueous solution, emulsion, or dispersion. The surface of the Yankee dryer is continuously sprayed with the creping adhesive while the cellulosic web is applied and dried by hot air impinging on the exposed side of the paper and conductive heat is transferred from the drum. As the paper dries, hydrogen bonds form between the fibers creating a flat and dense web morphology. The paper is then scraped backwardly upon itself and off of the Yankee dryer by means of a flexible blade, called a “doctor” blade or a “creping” blade. This creping process causes a substantial number of inter-fiber bonds to break, altering the physical-chemical characteristics of the web and increasing the perceived softness of the resulting creped product.
The art of obtaining good crepe quality relies on maintaining the proper level of adhesion between the paper web and the surface of the Yankee dryer. Inadequate adhesion can result in poor or non-existing creping or require lower speed operation due to slow drying, while excessive adhesion can lead to poor sheet quality or cause the sheet to break. Cellulosic webs that are insufficiently adhered to the Yankee dryer can impact the control of the web as it travels between the creping blade and the winder upon which a roll of the paper is being formed, causing problems in forming a uniform roll of paper. For example, a loose sheet between the creping blade and the roll can cause wrinkles, foldovers, and weaving of the edges of the sheet in the rolled-up paper, adversely affecting subsequent operations of paper manufacture. Release aids can alter the properties of the adhesive and further provide lubrication to the doctor blade, and influence the release of the paper web from the Yankee dryer, all of which can affect the properties of the creped product. Considerable effort has been spent trying to adjust the balance between the adhesion and the release of the web, while maintaining other conventional parameters that influence the creping process, such as web wetness and creping blade angle. A significant drawback with the existing creping adhesives is that the formulations of the creping adhesives generally need to be changed or adjusted when the wet end chemistry is changed (pH, reactive chemicals, debounders, etc.), the temperature profile is modified, or the residual moisture in the paper web is modified.
There is a need, therefore, for improved creping adhesives that can provide more control over the adhesion/release balance of the paper web to/from the surface of the dryer and methods for making and using same.